Printed and bound materials, such as magazines and the like, are typically produced on a binding line. Specifically, a plurality of packer boxes are disposed adjacent a gathering or binding chain wherein each packer box stores a plurality of signatures. The binding chain includes a plurality of chain pins defining chain spaces which are moved past the packer boxes. During such movement, the packer boxes are operated to feed signatures onto the chain spaces. The assembled signatures are then stitched, trimmed and prepared for shipment.
During operation of the binding system, defective books can be produced as a result of, for example, misfeeds of signatures, misalignment or improper positioning of gathered signatures and the like. A first drag (referred to as a "Higgins drag" by the assignee of the instant application) is carried by each packer box and includes a spring-loaded drag blade which contacts the signatures fed by the preceding packer boxes. A second drag is also carried by each packer box and is located downstream of the first drag and includes a drag which pulls the signature fed by the packer box against one of the chain pins so that the signatures are properly aligned in the chain spaces. In addition, a trailing portion of each Higgins drag includes a reflective surface and an opto-electronic sensor is mounted on each packer box and is directed at the reflective surface. The output of each opto-electric sensor is detected during a predetermined period in each packer box feeding sequence. If a signature has been properly placed on the chain by a packer box, the signature will cover the reflective surface during the predetermined period and the output of the sensor will be in a first state. On the other hand, if a signature has not been properly fed onto the chain, the reflective surface will not be covered during the predetermined period and the output of the sensor will be in a second state during such time. The output of the sensor is utilized by a controller to operate a reject gate downstream of the packer boxes if such a misfeed condition is sensed so that the defective group of signatures is removed from the binding line.
During the setup procedure for the binding line, individual packer boxes are either moved into or out of the binding line adjacent the chain. Often this movement of the packer boxes results in misalignment of and/or damage to the opto-electronic sensors and drags. Such misalignment and damage can result in erroneous fault detection due to improper electrical timing of the sensor. Also, the need to accurately position the sensors and drags undesirably increases the period of time needed to set up the binding line, and thus increases the down time between production runs.